template-haskell: Missing instances for Rational and ().

Test Plan: ./validate

Reviewers: austin

Reviewed By: austin

Subscribers: thomie, carter

Differential Revision: https://phabricator.haskell.org/D492
add missing instances for Loc and a few missing Eq instances

Summary: This adds a few missing instances that can be automatically derived

Reviewers: hvr, goldfire, austin

Reviewed By: goldfire, austin

Subscribers: thomie, carter

Differential Revision: https://phabricator.haskell.org/D495
Only test for bug #9439 when llvm is installed

Reviewers: bgamari, austin

Reviewed By: austin

Subscribers: thomie, carter

Differential Revision: https://phabricator.haskell.org/D500

GHC Trac Issues: #9807